The answer is that matching Phase 2 proposals between peers is one of the three essential conditions for IPsec Phase 2 to succeed. This is correct because IPsec Phase 2 negotiation, whether using IKEv1 Quick Mode or IKEv2, relies on Proxy IDs—specifically the local and remote subnet definitions—to establish the security associations that determine which traffic is protected. If these traffic selectors do not match on both ends, the exchange fails, and no Phase 2 SAs are created. On the Fortinet NSE 7 Advanced Security NSE7 exam, this concept tests your understanding of IPsec tunnel establishment beyond simple authentication; a common trap is assuming Phase 2 only needs matching encryption and authentication algorithms, when in fact mismatched proxy IDs are a frequent cause of failure. A useful memory tip is to think of Phase 2 as the "what traffic" negotiation—if the peers disagree on which subnets to protect, the tunnel cannot form.
NSE7 Advanced VPN and Zero Trust Practice Question
This NSE7 practice question tests your understanding of advanced vpn and zero trust. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which THREE conditions must be met for an IPsec VPN to successfully establish phase2?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Proxy IDs (local and remote subnets) match on both sides
Option A is correct because IPsec Phase 2 uses Proxy IDs (local and remote subnets) to negotiate the security associations (SAs) that define which traffic is protected. If the proxy IDs do not match on both peers, the IKEv1 or IKEv2 Quick Mode exchange will fail, preventing the establishment of Phase 2 SAs. This is a fundamental requirement for matching traffic selectors in the IPsec SA negotiation.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Proxy IDs (local and remote subnets) match on both sides
Why this is correct
Phase2 uses proxy IDs to define interesting traffic; they must match.
Related concept
Read the scenario before looking for a memorised answer.
✗
Firewall policies allow traffic between the subnets
Why it's wrong here
Firewall policies are not required for phase2 negotiation; they affect data traffic.
✓
Perfect Forward Secrecy (PFS) settings match if enabled
Why this is correct
If PFS is configured on one side, it must be enabled on the other with matching DH group.
Related concept
Read the scenario before looking for a memorised answer.
✓
Phase2 proposals match between peers
Why this is correct
Matching encryption and authentication algorithms are required.
Related concept
Read the scenario before looking for a memorised answer.
✗
NAT traversal is enabled on both sides
Why it's wrong here
NAT traversal is only needed if a NAT device is between peers; not a mandatory condition.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse firewall policy requirements with Phase 2 negotiation requirements, mistakenly thinking that firewall policies must allow traffic before Phase 2 can establish, when in fact Phase 2 only requires matching proxy IDs, proposals, and PFS settings.
Detailed technical explanation
How to think about this question
In IKEv1 Phase 2, the peers exchange Proxy IDs via the IDci and IDcr payloads in Quick Mode, which must match exactly for the IPsec SA to be created. If PFS is enabled, a new Diffie-Hellman exchange is performed in Phase 2, and the PFS group must match; otherwise, the SA negotiation fails. Phase 2 proposals (encryption, authentication, and lifetime) are also matched during this exchange, and any mismatch causes a NO_PROPOSAL_CHOSEN notification.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Advanced VPN and Zero Trust — This question tests Advanced VPN and Zero Trust — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Proxy IDs (local and remote subnets) match on both sides — Option A is correct because IPsec Phase 2 uses Proxy IDs (local and remote subnets) to negotiate the security associations (SAs) that define which traffic is protected. If the proxy IDs do not match on both peers, the IKEv1 or IKEv2 Quick Mode exchange will fail, preventing the establishment of Phase 2 SAs. This is a fundamental requirement for matching traffic selectors in the IPsec SA negotiation.
What should I do if I get this NSE7 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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